Customer Lifetime Value (LTV or CLV) is the total recurring revenue a customer is expected to generate over the entire duration of their subscription. The simplest formula is \(\text{LTV} = \text{ARPU} / \text{churn rate}\), using the same time period for both inputs. A more realistic version incorporates gross margin: \(\text{LTV} = (\text{ARPU} \times \text{gross margin}\%) / \text{churn rate}\). Because LTV scales inversely with churn (doubling churn approximately halves LTV), linearly with gross margin, and linearly with ARPU, each input is a powerful lever. The most accurate approach, when data allows, is cohort-based: sum the actual cumulative gross-margin revenue from a cohort and divide by the number of customers in it, replacing the formula's assumptions with observed behavior.
The companion metric is Customer Acquisition Cost (CAC), the total sales and marketing spend in a period divided by new customers added. The LTV:CAC ratio compares the lifetime value of a customer to the cost of acquiring them; 3:1 or higher is the common rule of thumb. Below 3:1 suggests the business may be under-investing in growth and leaving opportunity on the table, while below 1:1 is unsustainable—each customer costs more to acquire than they will return. CAC payback period is a related time-based measure: the number of months of gross-margin contribution required to recover CAC. Healthy benchmarks are under 12 months for SMB SaaS and under 18–24 months for enterprise SaaS, where longer sales cycles and higher touch costs are normal.
Gross margin is the bridge between LTV and unit economics. Typical B2B SaaS gross margins fall in the 70–85% range, reflecting the recurring, hosted nature of the product. Low-margin businesses recover CAC slowly because the same nominal revenue delivers less contribution per dollar, dragging down LTV. Gross margin subtracts only cost of goods sold—hosting, third-party APIs, payment processing, and often customer success and onboarding—while contribution margin goes further by also subtracting variable sales, marketing, and service costs. Cloud hosting alone often consumes 10–25% of revenue, depending on usage-based components and scale, so margin assumptions matter when modeling LTV. S&M efficiency (a period measure of spend vs new ARR) and LTV:CAC (a lifetime economic ratio) answer different but related questions about how well acquisition dollars are being deployed.